1. Field of the Invention
The present invention relates to a substrate accommodating tray pallet used for transporting and transferring a substrate, and a substrate transfer system using the substrate accommodating tray pallet. The substrate is a display glass substrate, for example, and used for a display panel of a liquid crystal display device or the like.
2. Description of the Related Art
A display panel for a liquid crystal display device usually includes a pair of display glass substrates opposed to each other and sealed together, and a liquid crystal material sealed between the pair of glass substrates. Recently, glass substrates having a thickness of 0.7 mm or less are widely used for such a display panel. As the glass substrates are increasing in size, the planar area of the glass substrates which are carried to the display panel production plants is increasing, and even glass substrates having a side length of 1.3 m or greater are used.
Such a large and thin glass substrate easily warps and tends to break. Thus, handling of the glass substrate is difficult. Therefore, there is a problem that it is impossible to transport a number of glass substrates with a high efficiency. In order to solve these problems, Japanese Laid-Open Publication No. 10-287382 discloses a substrate accommodating tray for accommodating one glass substrate. A substrate accommodating section of the substrate tray cassette has a lattice structure. The substrate accommodating tray is structured such that a plurality of substrate accommodating trays can be stacked vertically. Such a substrate accommodating tray allows a large and thin glass substrate to be accommodated without warping and thus without being broken during transportation. Since a greater number of substrate tray cassettes can be stacked vertically for transportation and storage, the space efficiency can be improved, and a number of glass substrates cab be transported efficiently.
When a plurality of substrate accommodating trays stacked vertically are transported, a number of vertically stacked substrate accommodating trays are usually mounted on a pallet for transferring into a truck and carrying into a production plant.
When a number of the substrate accommodating trays stacked are carried into a production plant, it is necessary to separate the vertically stacked substrate accommodating trays from each other to remove a glass substrate from each of the substrate accommodating trays. In order to remove a glass substrate from each of the substrate accommodating trays, the following method is employed, for example. Each of the substrate accommodating trays includes an opening on a bottom. Through the opening, a substrate removal tool which has a pin shape is inserted to raise a glass substrate accommodated in the substrate accommodating tray. The substrate is removed by a substrate transfer device which has an arm shape.
In such a case, it is necessary to separate the vertically stacked substrate accommodating trays one by one and to transfer the separated substrate accommodating trays to a position where the substrate removal tool is provided. Thus, the efficiency of the operation is low.
Furthermore, an opening provided on a substrate accommodating tray for inserting a substrate removal tool may allow dust and the like to enter the substrate accommodating tray during a transportation of the substrate accommodating tray. This may cause a glass substrate accommodated in the substrate accommodating tray to be contaminated.